In a small saucepan of boiling water over medium heat, cook the sweet potatoes for 10 minutes, or until soft. Drain into a colander, transfer to a plate, and mash with a fork.

Preheat a waffle iron to medium-high.

In a large bowl, whisk the eggs, buttermilk, coffee and butter until light and foamy.

With a large spoon, stir in the flour, sugar, baking powder, cinnamon, and vanilla. Continue to stir until the batter is smooth and the dry ingredients are well incorporated into the egg and butter-milk mixture. Fold in the mashed sweet potato and mix well.

Ladle enough batter into the preheated waffle iron to make 1 waffle. Typically, it takes about 3 minutes for a waffle to become crisp and golden. Continue with the remaining batter.

To jazz up plain maple syrup, simmer it over low heat with some chopped pecans and a dash of vanilla until very warm.